1. Field of the Invention
The invention relates to pneumatic tube systems and to carriers for such systems, and more particularly to the use of an adapter end closure which may be physically separated from a tubular material-conveying carrier to provide a means for reversing spacing between air seals held at either end of the tubular material-conveying carrier. The adapter unit is designed to house a unique camming arrangement for use in biasing an end closure for the carrier.
2. Description of the Prior Art
Prior art pneumatic tube system carries do not show a means of disengaging end portions from a tubular material-conveying carrier where the end portion as a unit includes not only the disclike end cap but also the entire pivoting mechanism for the end closure. Accordingly, prior art pneumatic tube system carriers are not designed to facilitate the quick and easy replacement or repositioning of the air seal ring which is normally found near each end of such carriers.
Prior art closure arrangements also do not provide a simple end closure biasing system suitable for use with a plastic cam and cam follower. Prior art cam biasing systems employ metal cams and followers frequently formed in the shape of an ellipse or parabola. The provision of an elliptical cam face for a plastic cam is impractical due to the limitations of the material. The applicants will disclose a simple and inexpensive cam biasing arrangement suitable for use in its adapter unit end closure.
A spring-biased toggle-connected mechanism contained in the cavity formed within an end closure to urge and hold the closure in either a fully closed or fully opened position is shown in the U.S. patent granted to Barnett, U.S. Pat. No. 3,788,577, granted on Jan. 29, 1974. This patent does not disclose a camming arrangement. Instead, a toggle mechanism operates within the plane of the disclike end closure. The only point of similarity is in Barnett's use of a pivot channel positioned at a circumferential edge of the disclike closure and perpendicular to the disclike closure for insertion into a wall of a tubular material-conveying carrier. Barnett does not provide for detaching an end piece from the tubular material-conveying carrier which end piece would contain the entire, fully assembled biasing mechanism.
Replaceable wear rings for use in providing an efficient seal during travel through a pneumatic tube are disclosed in the patent granted to Barnett, U.S. Pat. No. 3,787,008, granted on Jan. 22, 1974. Barnett discloses an annular shoulder formed on each end portion of a tubular material-conveying carrier against which a wear ring is seated and retained by a collar or retaining ring. However, the retaining ring is mounted by a press fit on the outer cylindrical surface of the tubular material-conveying carrier. While Barnett asserts that the retaining ring can be removed from the carrier body to replace the wear ring, it is clear that the retaining ring is destroyed in the process. This is because the retaining ring is preferably bonded by an adhesive and must itself be replaced in the process of changing the wear ring. The system devised by the applicants comprehend the repeated use of a spacer ring. The applicants' spacer ring is not a press fit, but, rather, is itself used to hold the end closure adapter unit against the end of the tubular material-conveying carrier. Barnett shows no species of a tongue and groove locking arrangement comparable to that comprehended by applicants.
A rod-like torsion bar for pivoting and holding the closure of a pneumatic tube carrier is disclosed in the patent granted to Delamater, U.S. Pat. No. 3,506,216, granted on Apr. 14, 1970. The torsion bar of this disclosure extends down the entire length of the tubular material-conveying carrier. The biasing action provided by the torsion bar causes the closure member to cam across an abutment end of the tubular material-conveying carrier in a toggle-like fashion. In the fully opened position, the closure member pivots freely on the torsion bar. The disadvantages of the carrier disclosed by Delamater is that the torsion bar provides little resistance to movement of the closure end axial to the tubular material-conveying carrier. The result is that the end closure rattles and is easily mispositioned so that the torsion bar is bent or otherwise damaged. Delamater does not disclose reversible, or even removable, air seal rings; nor does his pivot biasing arrangement lend itself to use in a self-contained end closure adapter unit such as that disclosed by the applicants.
Other toggle mechanisms for biasing disclike closure elements on a pneumatic tube carrier are shown in the patent granted to Anders, U.S. Pat. No. 3,701,497, granted on Oct. 31, 1972; and the patent granted to Roelandt, U.S. Pat. No. 3,556,436, granted on Jan. 19, 1971. These disclosures are quite similar in that they show a pivot shaft which is anchored in a side of the tubular material-conveying carrier. Both employ spring biasing toggle arrangements disposed within the plane of the disclike closure member. Both employ metal disc members on the inside edge of the disclike closure member in an effort to provide rigidity against axial vibration and dislocation. Anders also provides a pivot sleeve telescoped over the pivot shaft and journaled onto the pivot shaft. The substantial metal composition of these end closures obviously make them more difficult and expensive to manufacture. Also, no provision is made for removing the air seal; and the lid may not be separated from the tubular material-conveying carrier except by extracting retaining pins or screws from the wall of the tubular material-conveying carrier.
Early forms of biasing for pneumatic tube carrier closure members are illustrated by the patents to Erby, U.S. Pat. No. 1,807,834, granted on June 2, 1931; and to Pravda, U.S. Pat. No. 1,911,713, granted on May 30, 1933. These two patents are similar in that both employ a rod traversing the entire length of the tubular material-conveying carrier. In Erby, a lid attached to the rod is extracted from the inside of the tubular carrier and pulled up against the tension of a coil spring spiralling between a sleeve fixed to the wall of the tube and a keeper ring fixed to the bottom of the rod. Pravda accomplishes substantially the same thing by pushing down on a sliding top wall of the tubular carrier causing the closure member to be revealed and then rotated to one side. In Pravda, a coil spring pushes on an interior telescoping tube rather than on the pivoting rod itself. As in Delamater, the provision of a rod extending the length of the tubular carrier precludes separation of end adapters for the purpose of adjusting spacing between air seal rings.
In all of the references cited, the use of a substantial amount of metal parts and fittings increases the cost of production and the difficulty of repair. In all of the references cited, except Barnett, pivot pins or rods are easily damaged by bending or breaking when the disclike end closure is in the open position. In all of the references cited, the pivot pin is anchored in a wall of the tubular material-conveying carrier by means of retainer pins or screws. Such means of anchoring the pivot pins prevents the easy removal of the end closure as a fully assembled unit and increases the likelihood that the entire tubular carrier will be cracked or otherwise damaged by stresses suffered by the closure disc when such disc is in the open position.
The applicants' pivot pin is not constrained against rotation by any retainer pins or screws. It serves merely as an axis of rotation for the cam and as a travel shaft for the cam follower in conjunction with a small helical spring spiralling around the pivot shaft between the sliding cam follower and a keeper ring and spring clip securing the pivot pin against axial dislocation.
In summary, none of the prior art references show an end closure unit which may be separated from the tubular carrier as a unit without the use of any tools whatsoever. Also, none of the prior art references show a reversible air seal ring capable of assuming two distinct spacings. The prior art discloses various forms of spring-loaded lid closure means which hold a disc-shaped lid in either open or closed position. While none of the patents reviewed show a spring-loaded cam arrangement similar to that about to be disclosed by the applicant, commercially available devices made by Security and Mosler use a spring-loaded cam arrangement employing machined steel parts rather than the cheaper molded plastic materials made possible by the applicants' novel configuration of such a spring-loaded cam arrangement.